Power battery pack is responsible for storing and supplying power. In use, it is necessary to design an insulation detection circuit for the power battery pack to monitor whether the insulation resistance values of the positive electrode and the negative electrode of the power battery pack meets standards, thus avoiding security issues due to failure of the insulation resistance values of the positive electrode and the negative electrode of the power battery pack in meeting the standards.
Currently, in the insulation detection circuit, the power battery pack and a sampling unit are set in non-common-ground-connection. Non-common-ground-connection means that the positive electrode and the negative electrode of the power battery pack are grounded with high voltage, and the sampling unit is grounded with low voltage. An isolation unit is provisioned after the sampling unit, in order to isolate interference from a high voltage grounded signal of the power battery pack to a sampled signal of the sampling unit.
However, inventors of the present application have found that the isolation unit of the prior art also introduces a new interference signal while isolating the high voltage grounded signal of the power battery pack, resulting in a decrease in the accuracy of the sampled signal.